#clojure – 2016-03-09

2016-03-09

00:27	TEttinger	TimMc: you have no idea how often I use toBinaryString and toHexString, haha
00:27	TEttinger	I use a lazybot as a calculator and any binary stuff needs that
00:58	ilevd	Hi, I find strings like "{{#list}}" "{{#render}}" in Java project html files, what's that framework or lib?
01:08	rhg135	Mustache
01:12	ilevd	Thanks a lot!
01:36	AndreasO	(run :dispose), what does it do?
01:40	ilevd	It depends on library, where is this used?
01:47	AndreasO	In a seesaw example.
01:52	TEttinger	AndreasO: depends on what run is
01:54	TEttinger	in all the examples I see that's commented out, AndreasO
01:55	TEttinger	it looks like defexample defines the run fn https://github.com/daveray/seesaw/blob/master/test/seesaw/test/examples/example.clj
01:58	AndreasO	TEttinger: strange, I found an example here it wasn't commented out
01:59	TEttinger	it looks like (run :dispose) will run the example, and when the example is closed it calls whatever fn is assigned to :dispose in the defexample
02:00	TEttinger	that's only in the examples
02:13	AndreasO	https://github.com/juliangamble/clj-seesaw-examples/blob/master/src/seesaw/test/examples/clock.clj
02:13	AndreasO	There it is, not commented out.
02:56	ilevd	Are you happy with Clojure?
02:58	opqdonut	it's nice enough
02:58	ridcully_	for the larger part
03:00	TEttinger	yes
04:15	prohobo	clojure is hard yo
05:04	prohobo	anyone know how to dynamically add a field to the frame using seesaw?
05:18	prohobo	hello?
05:18	clojurebot	BUENOS DING DONG DIDDLY DIOS, fRaUline prohobo
05:21	prohobo	god damn you clojurebot
05:21	saureb	lol
05:24	krl	is there any way to see where clojure looks for java .class files to import? I'm getting class not found, even though the .class i'm including seems to be in the right place, (pointed to by :java-source-paths)
05:25	krl	(in lein)
05:30	Empperi	it uses the classpath declaration
05:30	Empperi	which is passed for java on startup
05:32	krl	can you dump it somehow from the repl?
05:34	Empperi	(System/getProperty "java.class.path")
06:45	amoe_	anyone know how to move files using raynes.fs library? It seems to have support for moving things, but I don't know how to get access to the 'move' function that is used by these tests. https://github.com/Raynes/fs/blob/master/test/me/raynes/core_test.clj#L425
06:58	jonathanj	amoe_: according to the source, that function is only available if you're running java 7+
07:04	amoe_	jonathanj: I am indeed running java 7
07:08	jonathanj	amoe_: Looks like that function isn't in 1.4.6, which is the latest stable release: https://github.com/Raynes/fs/blob/1.4.6/src/me/raynes/fs.clj
07:09	jonathanj	rather, it's the version the README says to use
07:09	jonathanj	looks like it was added quite a long time ago: https://github.com/Raynes/fs/commit/fdab09a711f6fd457bcdf13d213c6dea79c31241
07:10	amoe_	oh, that makes sense, thanks! I will find a workaround.
07:11	jonathanj	maybe file an issue about releasing a new version?
07:11	amoe_	jonathanj: yup, I will do so.
07:12	amoe_	oh, actually one already exists https://github.com/Raynes/fs/issues/102
07:13	amoe_	it's funny, since starting to work with clojure half the issues I hit are open and resolved in the last ~2 months or so... seems the ecosystem is buzzing
07:32	prohobo_	im not getting any closure on my seesaw issue
07:33	prohobo_	i am emotionally exhausted
07:41	amoe_	prohobo_: maybe paste the code?
07:42	prohobo_	nah, its okay
07:42	prohobo_	im too tired to deal with it today
08:21	amoe_	I wonder is there any way to use the arrow syntax to immediately create a binding with the result, I want to write something like (-> (large-operation) (bind var (do-something var) (do-something-else var)))
08:21	amoe_	I know that's basically a function but I'd like to avoid making another function as it's in a test
08:23	Kneiva	There is nothing wrong in making a function just for a test.
08:24	amoe_	Kneiva: just my taste but I prefer to keep test code as flat as possible
08:43	TMA	amoe_: you can use unnamed functions: ((fn [var] (do-something var) (do-something-else var)) (large-operation)) or a (let [var ...] ...)
09:00	Malnormalulo	amoe_: If you reeeeeally want to avoid non-test namespace-accessible artifacts, you could always just make liberal use of `letfn`
09:01	Malnormalulo	which can, itself, contain test defs, so that your tests become closures
09:06	TimMc	amoe_: Is the issue that your tests :use the ns under test, and you don't want to risk testing a test fn of the same name as a var from the original ns?
09:15	zenoli	l.*
09:15	zenoli	Whoops, sorry.
09:56	RedNifre	Clojure newbie here. So someone mentioned this nice pattern matching library yesterday. I guess I can figure out how to use it in a leiningen project but how can I test it in the REPL? https://clojars.org/defun/defun
09:57	egli	RedNifre: maybe with lein-try
09:57	egli
09:58	egli	https://github.com/rkneufeld/lein-try
10:05	RedNifre	Thanks, but that link gives me other ideas. It mentions a project.clj in ~/lein that I don't have... I guess I'll learn more about lein before customizing it further.
10:05	RedNifre	Bookmarked for later, thanks egli.
10:08	RedNifre	I think it was justin_smith who mentioned a mutable map that maps symbols to values or functions (or macros even?), e.g. using (def pi 3) writes to one such map. Are these maps the namespaces? Or are there differences?
10:24	sdegutis	You ever have a day or week where you're like insanely productive compared to every other day?
10:25	RedNifre	sdegutis. Rarely. It's usually the opposite where one problem leads to the next and everything that should be simple is complicated.
10:25	sdegutis	:D
10:27	RedNifre	So what are you being productive about today? :)
10:27	Malnormalulo	"My first build failed this morning so I've just been staring at the stack trace until noon" --me, most days
10:27	sdegutis	RedNifre: using Clojure at work
10:27	Malnormalulo	wait stack trace in a build that doesn't even make sense
10:27	sdegutis	Malnormalulo: haha yes I know that feeling
10:36	RedNifre	Hm, do the dots in namespaces mean anything?
10:40	Malnormalulo	I think, under the covers, in the bytecode, they're the same as dots in Java packages. If that means anything to you
10:41	Malnormalulo	(And if you're using the JVM implementation of Clojure)
10:42	RedNifre	Ah, so I could :require many things at once by doing (:require [clojure.*]) ?
10:45	Malnormalulo	That...sounds plausible. I've never tried it.
10:46	prohobo_	damn, clojure. you scary
10:49	mavbozo	RedNifre, you require many things at once by doing (:require [foo.bar :refer [fun1 fun1 fun3 var1 var2]])
10:49	RedNifre	u-huh... So the dots in the namespace name are less important in clojure, they are more informal?
10:50	mavbozo	the dots in the namespace are important to separate namespace segment
10:52	luma	if you want to require multiple namespaces with the same prefix, you can do (:require (foo.bar baz bloo)), which would require both foo.bar.baz and foo.bar.bloo
10:52	RedNifre	Ah, I see.
10:53	luma	and the usual tricks work there as well: (:require (foo.bar [baz :refer [fn1 fn2]] bloo))
11:01	RedNifre	Hm, the JoC book just warned me about java boolean objects i.e. (Boolean. "false"). It says the safe way is (Boolean/valueOf "false"). How exactly does that work? Is Clojure's false a java Boolean object? Or the primitive? Or is there autoboxing?
11:02	mavbozo	,(type false)
11:02	clojurebot	java.lang.Boolean
11:02	RedNifre	,(type nil)
11:02	clojurebot	nil
11:02	wink	RedNifre: https://clojurebridge.github.io/community-docs/docs/clojure/truthiness/
11:03	RedNifre	Thanks wink. I'm currently reading about truthiness.
11:03	mavbozo	,(class false)
11:03	clojurebot	java.lang.Boolean
11:04	RedNifre	So the only falsey things are nil and false, where nil is Java's null and false is Java's Boolean object for false. Do the primitive java booleans show up in Clojure as well or do they always get autoboxed to Boolean objects before showing up in Clojure?
11:12	RedNifre	Now JoC says that my functions should expect to be called with nil if they expect collections and that I should use seq to be sure. That advice seems strange to me, I would have thought that treating nils as empty collections (instead of as bugs) would obfuscate bugs elsewhere in the code. Why is that a good idea?
11:22	bermraj	good morning, is there a dirrerence in using (Integer.) compare to (new Integer)?
11:23	RedNifre	Yes, the JVM caches the first 255 Integers. I guess it doesn't do that when calling the constructor.
11:23	RedNifre	Wait, what does (new Integer) mean in Clojure?
11:24	RedNifre	(Newbie here. I just learned that (Integer.) calls the constructor so I wonder what (new Integer) means)
11:32	rcassidy	,(new Integer)
11:32	clojurebot	#error {\n :cause "No matching ctor found for class java.lang.Integer"\n :via\n [{:type clojure.lang.Compiler$CompilerException\n :message "java.lang.IllegalArgumentException: No matching ctor found for class java.lang.Integer, compiling:(NO_SOURCE_PATH:0:0)"\n :at [clojure.lang.Compiler analyzeSeq "Compiler.java" 6875]}\n {:type java.lang.IllegalArgumentException\n :message "No matching ct...
11:34	narwhal01	hi guys
11:34	mavbozo	,(new Integer 1)
11:34	clojurebot	1
11:34	mavbozo	,(class (new Integer 1))
11:34	clojurebot	java.lang.Integer
11:34	RedNifre	,(= 1 (new Integer 1))
11:34	clojurebot	true
11:34	narwhal01	,(clojure.string/join " " ["I" "'m" "sorry"])
11:34	clojurebot	"I 'm sorry"
11:35	RedNifre	heya
11:35	narwhal01	how can i join with condition if the word "'m" don't join with space else join with space
11:36	rcassidy	,(Integer. 3)
11:36	clojurebot	3
11:36	RedNifre	narwhal01 funny idea: join with space and then replace " '" with "'"?
11:37	RedNifre	more serious idea: something something foldr / reduce ?
11:37	narwhal01	RedNifre, is the better idea?
11:37	narwhal01	RedNifre, reduce ?
11:38	RedNifre	yeah, reduce with a string builder I think.
11:38	narwhal01	ah ok
11:50	mavbozo	RedNifre, in what chapter in JoC book there is a advice that "my function should expect to be called with nil if the function expect collections"?
11:53	RedNifre	mavbozo hang on, let me go back...
11:54	RedNifre	mavbozo It's in 3.2
11:55	RedNifre	hang on
11:55	RedNifre	I think I might have missread that.
11:56	RedNifre	Oh right, it says "you shouldn't assume seq has been called on your collection arguments, but instead call seq in the function itself." So it means I'll receive empty collections and shouldn't check them for truthiness without calling seq.
11:57	RedNifre	thanks mavbozo
11:59	rcassidy	,(seq nil)
11:59	clojurebot	nil
12:00	mavbozo	,(seq '())
12:00	clojurebot	nil
12:00	RedNifre	,(seq ())
12:00	clojurebot	nil
12:01	MJB47	does anyone know why people dont use empty?
12:01	MJB47	other than its 3 chars longer
12:01	RedNifre	The books says it's because you would have to type "(when-not (empty?" instead of "(when (seq".
12:02	mavbozo	that's 7 chars longer
12:03	RedNifre	,(vec [])
12:03	clojurebot	[]
12:03	RedNifre	Hm, so no nil here...
12:04	RedNifre	,(vec (seq []))
12:04	clojurebot	[]
12:08	mavbozo	the comprehensive explanations on sequence is in chapter 5.1 in JoC book
12:10	RedNifre	I'll get there eventually.
12:56	cortexman__	oooo\\\\\/
12:57	RedNifre	Hm, JoC says that "underflow" means a floating point becoming zero. I thought it meant substracting from a negative int and getting a positive one as a result.
12:57	RedNifre	Is Integer.MIN_INT -1 also called an "overflow"?
12:59	justin_smith	RedNifre: maybe underflow, but I think it throws OverflowError
12:59	justin_smith	,(dec Integer/MIN_VALUE)
12:59	clojurebot	-2147483649
12:59	justin_smith	err
12:59	justin_smith	,(dec Long/MIN_VALUE)
12:59	clojurebot	#error {\n :cause "integer overflow"\n :via\n [{:type java.lang.ArithmeticException\n :message "integer overflow"\n :at [clojure.lang.Numbers throwIntOverflow "Numbers.java" 1501]}]\n :trace\n [[clojure.lang.Numbers throwIntOverflow "Numbers.java" 1501]\n [clojure.lang.Numbers dec "Numbers.java" 1851]\n [sandbox$eval49 invokeStatic "NO_SOURCE_FILE" 0]\n [sandbox$eval49 invoke "NO_SOURCE_FIL...
12:59	justin_smith	yeah, it calls it an overflow though it's an underflow technically
13:00	justin_smith	https://en.wikipedia.org/wiki/Arithmetic_underflow
13:00	RedNifre	Can you divide the double that is closest to zero by two for me?
13:00	justin_smith	RedNifre: oooh
13:00	justin_smith	one moment
13:01	justin_smith	,(/ (Math/ulp 0.0) 2)
13:01	clojurebot	0.0
13:01	RedNifre	okay, the wikipedia article calls both the integer thing and the float becomes zero thing an "underflow" where the JoC book claims that only dividing a float and getting zero is called an underflow.
13:01	RedNifre	Hm.
13:01	RedNifre	So no underflow exception there...
13:01	justin_smith	RedNifre: Math/ulp gives the closest non-equal value to a given double
13:01	justin_smith	RedNifre: that's not an underflow
13:02	justin_smith	it's a precision failure, but IEEE floats don't throw on precision errors
13:02	RedNifre	,(Math/ulp 0.0)
13:02	clojurebot	4.9E-324
13:02	RedNifre	Right, I was surprised as well, but both JoC and the Wikipedia article call those underflows.
13:02	justin_smith	RedNifre: oh wait I'm wrong
13:02	justin_smith	underflow is about small numbers, not low negative numbers
13:02	justin_smith	d'oh
13:03	justin_smith	RedNifre: yeah, JoC is right, not me
13:03	RedNifre	Now you're agreeing with the book, but the wikipedia article says that low negative numbers also underflow.
13:03	justin_smith	now I am double confused, time for my morning coffee
13:03	justin_smith	haha
13:04	justin_smith	RedNifre: reading more closely, the wikipedia article is talking about negative digits on the exponent, not about negative numbers of high magnitude per-se
13:05	RedNifre	Oh right.
13:05	RedNifre	I guess an Integer can overflow at both ends then, but never underflow.
13:06	justin_smith	yeah, that sounds right
13:07	justin_smith	RedNifre: I don't know if anyone else replied about namespaces with mutable maps but the namespace owns a mutable map of symbols to vars (and each var is a mutable container holding a single value), but the namespace also has a map of referred bindings belonging to other namespaces, and probably some other junk too
13:08	justin_smith	eg. the stuff that makes require and use and import work
13:08	RedNifre	Ah, so a namespace is a bundle of several maps where each map has a different purpose?
13:10	justin_smith	yeah - it would probably be informative to check out the java code for this
13:11	RedNifre	I hope I'll understand Clojure as deeply as I understand Io (A dead language, the Lisp of the OOP world).
13:11	justin_smith	I remember Io, I never played with it though
13:11	justin_smith	what about smalltalk, that isn't the Lisp of OOP?
13:12	faxmodem	for all I know Io is a moon
13:12	RedNifre	In Io, everything is an object, the commands you type in the REPL are method calls on the REPL object, Objects are basically maps from Strings to other objects, when you do obj.bla = 5 you are really doing obj.setSlot("bla", 5) etc.
13:13	justin_smith	RedNifre: aha in smalltalk the equivalent of obj.bla = 5 sends a message of [set blah 5] to obj (everything is a message)
13:14	justin_smith	but for some reason at some point in programming history people decided OO was more about inheritence than it was about messages
13:15	RedNifre	Yeah, but in Io, when a method gets called instead of receiving its parameters in can choose to receive a call object instead.
13:15	RedNifre	It's also homoiconic, so the call object will contain the AST of what was passed as parameters.
13:15	RedNifre	This is basically as powerful as macros.
13:15	justin_smith	cool
13:16	RedNifre	And there's an operator table that you can inspect and modify.
13:16	RedNifre	It's both simple and brilliant. Unfortunately it's a dead language and I prefer FP over OOP these days so I'm looking at Clojure now.
13:17	alisdair	Io was great, it's a shame it never took off
13:20	RedNifre	Yeah. You can even turn Clojure syntax into valid Io syntax by defining a method with an empty name that transforms the passed AST before executing. You know, like this: https://gist.github.com/RedNifre/50a98c5ab07b526ca891
13:20	mmastic	What's the idiomatic way to create getters for maps? I'm finding myself making lots of stuff like `(def x (partial :x))'. I thought about a macro but I figured that if this was the way for such a common thing then it would surely be part of the core library.
13:20	justin_smith	mmastic: the idiomatic thing is to not use getters for things that are immutable
13:21	RedNifre	why not just :x?
13:21	justin_smith	exactly, what RedNifre said
13:21	justin_smith	with mutable things, that layer of information hiding can be very important, with immutable ones, it's much less useful
13:22	mmastic	I don't want plain keyword because it bit me in the ass earlier x_x it makes it impossible to change the map without breaking something.
13:22	amalloy	mmastic: def the keywords you want to use
13:23	amalloy	(def size :size) ... (size the-map)
13:23	amalloy	then if you change the name of the key, the compiler will know when you forget to update a use
13:23	RedNifre	Ah.
13:24	RedNifre	Maybe using records instead of maps would provide that type of security?
13:24	mmastic	It's very repetitive and boilerplate-y though, don't you think? and usually changing the name of the key isn't the issue, it's different structuring and such.
13:25	justin_smith	mmastic: my solution to that is typically to use prismatic/schema at system boundaries
13:25	mmastic	Yeah I thought about records, but I want to be able to extend on the fly.
13:25	justin_smith	mmastic: you can add any key to a record
13:25	RedNifre	that sounds like contradicting requirements.
13:26	mmastic	Prismatic/schema? what do you mean?
13:26	RedNifre	"prismatic" sounds like lenses and prisms...?
13:26	RedNifre	,(:not-there {})
13:26	mmastic	Oh, it does RedNifre :P what I mean is that I'm still molding my structure but I want to keep the solid part solid.
13:26	clojurebot	nil
13:27	justin_smith	mmastic: RedNifre: prismatic (which changed names recently) has a library called schema
13:27	justin_smith	it allows checking arbitrary facts about the shape of data, as a kind of dynamic type checking
13:28	mmastic	Ah libraries, okay. Hmm tbh that sounds like a bit of an overkill. Perhaps I should resort to macros anyway :P?
13:31	RedNifre	I would use maps as long as you can remember the keywords and switch to a record (or type?) when you get bitten :)
13:31	RedNifre	(Disclaimer: I have never used maps, types, records so far, I'm just starting out. Don't believe anything I say!)
13:33	mmastic	Hehe fair enough :P thank you. I might do that when I get more far ahead in the evolution of the data.
13:33	mmastic	Thank you everybody ^^ much appreciated.
13:34	RedNifre	Hang on.. Ruby has something called an ostruct.
13:34	RedNifre	That sounds like what you want.
13:34	RedNifre	You can add arbitrary keys to it, but when you try to retrieve an undefined one you get an error (I think).
13:34	RedNifre	Maybe something like that exists for Clojure?
13:35	justin_smith	RedNifre: this is what records do
13:35	justin_smith	except for the error part
13:35	justin_smith	,(defstruct Foo [a])
13:35	clojurebot	#error {\n :cause "Unable to resolve symbol: a in this context"\n :via\n [{:type clojure.lang.Compiler$CompilerException\n :message "java.lang.RuntimeException: Unable to resolve symbol: a in this context, compiling:(NO_SOURCE_PATH:0:0)"\n :at [clojure.lang.Compiler analyze "Compiler.java" 6688]}\n {:type java.lang.RuntimeException\n :message "Unable to resolve symbol: a in this context"\n ...
13:36	justin_smith	,(defrecord Foo [a])
13:36	clojurebot	#error {\n :cause "clojure.lang.Var cannot be cast to java.lang.Class"\n :via\n [{:type java.lang.ClassCastException\n :message "clojure.lang.Var cannot be cast to java.lang.Class"\n :at [clojure.lang.Namespace referenceClass "Namespace.java" 129]}]\n :trace\n [[clojure.lang.Namespace referenceClass "Namespace.java" 129]\n [clojure.lang.Namespace importClass "Namespace.java" 158]\n [clojure....
13:36	RedNifre	huh?
13:36	justin_smith	that error is weird...
13:36	justin_smith	RedNifre: huh? about which part?
13:37	RedNifre	Also, I take back what I said about ostruct, it just returns nil when you query something that's not inside.
13:37	justin_smith	,(defrecord Bar [a])
13:37	clojurebot	sandbox.Bar
13:37	justin_smith	,(assoc (Bar. 0) :b 1)
13:37	clojurebot	#sandbox.Bar{:a 0, :b 1}
13:37	justin_smith	that's it, that's what records do
13:38	RedNifre	,(:a (Bar. 0))
13:38	clojurebot	0
13:38	RedNifre	,(:c (Bar. 0))
13:38	clojurebot	nil
13:38	mmastic	Okay so I'll just use defs for now and worst case scenario I'll write a macro. Thanks again ^^
13:39	justin_smith	,(:c (assoc (Bar. 0) :c 2))
13:39	clojurebot	2
13:39	RedNifre	yeah, but mmastic's problem is that she/he wants a compiler check to catch that.
13:39	justin_smith	,(:c (map->Bar {:a 0 :c 2}))
13:39	clojurebot	2
13:39	RedNifre	,(:i-cantt-type (assoc (Bar. 0) :i-cant-type "huh"))
13:39	clojurebot	nil
13:40	justin_smith	right
13:40	justin_smith	that's why I was saying prismatic/schema, it's the right thing in the clojure world for checking those sorts of things
13:41	justin_smith	that or core.typed, but core.typed is a little trickier to integrate with
13:42	mmastic	Oh I don't care for a compiler check. I just want getters without boilerplate ^^ I basically want something to write the getter functions for me.
13:42	RedNifre	Are keywords getter function or is there some hidden macro that turns (:bla someMap) into (get someMap :bla)?
13:42	RedNifre	mmastic but why do you need a getter function if not for compiler checks?
13:43	mmastic	Yeah, they are.
13:43	mmastic	And an associative (such as a map) is also a function that takes a key and does the same thing.
13:43	RedNifre	Are keywords variadric functions that when called without arguments return themselves, otherwise call (get param self) ?
13:44	justin_smith	yeah, keywords are getters, and schema allows making assertions about which keywords are present (and the type / shape of the values under those keywords)
13:44	justin_smith	RedNifre: they have no way of returning themselves, though in the reader they are self-evaluating (but that is not the same as returning self when called)
13:45	hiredman	no
13:45	justin_smith	they do have an optional not-found argument when invoked though (the same not-found that get allows)
13:45	hiredman	,(:foo)
13:45	clojurebot	#error {\n :cause "Wrong number of args passed to keyword: :foo"\n :via\n [{:type java.lang.IllegalArgumentException\n :message "Wrong number of args passed to keyword: :foo"\n :at [clojure.lang.Keyword throwArity "Keyword.java" 97]}]\n :trace\n [[clojure.lang.Keyword throwArity "Keyword.java" 97]\n [clojure.lang.Keyword invoke "Keyword.java" 110]\n [sandbox$eval208 invokeStatic "NO_SOURCE_F...
13:48	mmastic	Hmm perhaps I'll explain what actually happened to me. I'm writing a graphical framework. An object in this system is a map, and it has a map assoced with :position which is a map with :x and :y. Then I introduced a physics engine, and the (-> object :position :x) turned into (-> object :physics :position :x). A caller that relied on the initial version broke, as you can imagine. So I thought to make getters. But now getters are boil
13:50	TimMc	mmastic: Cut off at "boil"
13:51	TimMc	(IRC has message length limits)
13:53	RedNifre	,::sandbox
13:53	clojurebot	:sandbox/sandbox
13:54	RedNifre	Just to be sure, that's a totally normal keyword named "sandbox/sandbox", right? The part that looks like a namespace is only informal to help programmers, it has no function whatsoever, right?
13:54	justin_smith	mmastic_: have you considered a protocol with a get-x method? that way you can extend the protocol for any object that should have an x coordinate, and the lookup of the actual property is defined in one place per Class
13:55	justin_smith	RedNifre: yeah, the namespace part is useful (eg. helps track who would be interested in that part of the data) but doesn't effect much - the namespace of the keyword doesn't even need to exist
13:55	justin_smith	,:akldjfalkdsjflakdsjfladskjflkadsjf/foo
13:55	clojurebot	:akldjfalkdsjflakdsjfladskjflkadsjf/foo
13:56	RedNifre	Yeah, so in the technical sense it's a regular keyword that just happens to have a slash in the middle.
13:56	mmastic_	Yeah I did but I'm not sure how would that be implemented. Would I reify instances or just extend maps? Hmm I actually just considered reifying which didn't sound good, but extending maps should work, I suppose, right? or am I missing something?
13:56	justin_smith	,(namespace :akldjfalkdsjflakdsjfladskjflkadsjf/foo)
13:56	clojurebot	"akldjfalkdsjflakdsjfladskjflkadsjf"
13:57	justin_smith	mmastic_: you would use a record, which is just a map that allows arbitrary protocols / interfaces to be implemented
13:57	RedNifre	so... what would I do with the namespace of a symbol?
13:57	justin_smith	,(namespace 'foo/bar)
13:57	clojurebot	"foo"
13:58	RedNifre	I meant keyword.
13:58	mmastic_	But I can't arbitrarily assoc new keys without going back and forth, right? that's a concern for me.
13:58	justin_smith	RedNifre: I just did that above
13:58	RedNifre	Yeah, I was asking what I can do with that.
13:58	justin_smith	mmastic_: false, you can associate any keys you want to a record
13:58	justin_smith	mmastic_: I already demonstrated that above
13:59	justin_smith	RedNifre: ahh, sorry, misunderstood
13:59	justin_smith	RedNifre: you might want to go through a map or set and collect keys matching a certain namespace
13:59	mmastic_	Oh really? damn, I got records wrong all along then :P I'll revisit them. So semantically they're just maps where some keys are specialized?
13:59	justin_smith	or remove them, or update them, etc.
14:00	justin_smith	mmastic_: plus the ability to implement interfaces and protocols, yes
14:00	justin_smith	they are very useful
14:00	TimMc	A word of warning, they can interfere with interactive development.
14:01	mmastic_	Omg that sounds amazing. Home come they can interfere?
14:01	justin_smith	(not= (defrecord Foo [a]) (defrecord Foo [a])) - they have the same name and slots, but are different classes
14:02	TimMc	If you make an instance, reload your code, then ask "is this object an instance of this record?" it will say "no", but it will still be of a class with the same name.
14:02	TimMc	and of course if you implement protocols everything goes haywire with code reloading, but you already get that with protocols
14:02	TimMc	(who makes wire out of hay anyhow)
14:02	justin_smith	my common approach to this is to put the record and protocol definitions in tiny namespaces that contain no logic that I never reload
14:03	justin_smith	but yes, these things are annoying to be sure
14:03	RedNifre	,(def a-symbol 'some-symbol)
14:03	clojurebot	#'sandbox/a-symbol
14:03	RedNifre	,a-symbol
14:03	clojurebot	some-symbol
14:03	mmastic_	Oh I see. I'll revisit records right now. Thank you!
14:03	RedNifre	,(resolve a-symbol)
14:03	clojurebot	nil
14:04	RedNifre	,(resolve 'a-symbol)
14:04	clojurebot	#'sandbox/a-symbol
14:04	RedNifre	What exactly does the "#'" at the start mean?
14:04	justin_smith	,(def some-symbol "found it")
14:04	clojurebot	#'sandbox/some-symbol
14:04	justin_smith	,@(resolve 'a-symbol)
14:04	clojurebot	some-symbol
14:04	justin_smith	,@(resolve 'some-symbol)
14:04	clojurebot	"found it"
14:05	justin_smith	,@(resolve @(resolve 'some-symbol))
14:05	clojurebot	#error {\n :cause "java.lang.String cannot be cast to clojure.lang.Symbol"\n :via\n [{:type java.lang.ClassCastException\n :message "java.lang.String cannot be cast to clojure.lang.Symbol"\n :at [clojure.core$ns_resolve invokeStatic "core.clj" 4239]}]\n :trace\n [[clojure.core$ns_resolve invokeStatic "core.clj" 4239]\n [clojure.core$ns_resolve invokeStatic "core.clj" 4229]\n [clojure.core$re...
14:05	justin_smith	ergh
14:05	justin_smith	,@(resolve @(resolve 'a-symbol))
14:05	clojurebot	"found it"
14:05	justin_smith	haha
14:05	RedNifre	What's with the @ again? And what's with the # in the output?
14:05	justin_smith	RedNifre: watch
14:05	justin_smith	,#'foo
14:05	clojurebot	#error {\n :cause "Unable to resolve var: foo in this context"\n :via\n [{:type clojure.lang.Compiler$CompilerException\n :message "java.lang.RuntimeException: Unable to resolve var: foo in this context, compiling:(NO_SOURCE_PATH:0:0)"\n :at [clojure.lang.Compiler analyzeSeq "Compiler.java" 6875]}\n {:type java.lang.RuntimeException\n :message "Unable to resolve var: foo in this context"\n ...
14:05	justin_smith	oops
14:06	justin_smith	,'#'foo ; I meant this
14:06	clojurebot	(var foo)
14:06	RedNifre	Oh, is that the lambda again?
14:06	justin_smith	,'@#'foo ; I meant this
14:06	clojurebot	(clojure.core/deref (var foo))
14:06	justin_smith	nope, anything starting with # is a reader-macro, and you can see the expansion by using '
14:06	justin_smith	so the above expansions via ' help?
14:07	RedNifre	ehm
14:07	justin_smith	RedNifre: #'foo is a shortcut for (var foo)
14:07	justin_smith	@foo is a shortcut for (deref foo)
14:08	RedNifre	,(resolve 'a-symbol)
14:08	clojurebot	#'sandbox/a-symbol
14:09	RedNifre	Okay, so clojurebot means (var sandbox/a-symbol) ?
14:09	justin_smith	right
14:10	RedNifre	hang on
14:10	RedNifre	I had to look up var :)
14:11	matt______	hey, all. i've used clojure for some time now, and i've always known that vectors are not seqs, but i've never understood why. when you call first on a vector, it calls RT's first, which turns it into a seq and then calls seq's first. can anyone explain or point me to an explanation?
14:11	TimMc	~colls and seqs
14:11	clojurebot	Cool story bro.
14:11	TimMc	hmm
14:11	RedNifre	Well, (def x 42) creates a var... but I don't understand that. Hm.
14:11	TimMc	~seqs and colls
14:11	clojurebot	seqs and colls is http://www.brainonfire.net/files/seqs-and-colls/main.html
14:11	TimMc	matt______: ^ I wrote this up a while back
14:12	matt______	TimMc: nice, thanks. checking it out now.
14:12	justin_smith	RedNifre: namespaces contain a hash-map from symbols to vars, each var is a mutable container holding a single value (with optional metadata)
14:12	TimMc	Summary: Seqs are views into collections.
14:12	RedNifre	I thought that (def x 42) adds an "x" entry to the namespace's map that points to 42. Where does (var 42) come in?
14:12	RedNifre	ah. why is that extra indirection needed?
14:12	justin_smith	RedNifre: because we want to hold onto the var and see the new value later
14:13	justin_smith	without looking it up in the namespace map every time
14:13	justin_smith	it's a thing that makes interactive development work as expected
14:13	matt______	TimMc: quick other question: ISeq also has a more function that no one seems to talk about. any reasoning behind that? deprecation via ignoring?
14:14	hiredman	inlining through a hashmap lookup is complicated, inlining a var deref is simpler
14:14	RedNifre	Oh, you mean if I do (def a "a") (def b a) (def a "not-a"), then b will return "not-a"?
14:14	hiredman	no
14:14	justin_smith	no, but inside a function that uses a, it would see the new a
14:14	hiredman	a is derefed and the value is stored in b
14:14	justin_smith	so (def b [] a) would work as you described
14:14	justin_smith	err, (defn b [] a)
14:15	RedNifre	You mean (def b a) checks the namespace map for a and finds a variable, takes the string out ouf that variable, creates a new variable and puts the string in it and then puts that newly created variable in the namespace map under b?
14:16	hiredman	you are mingling what happens at compile time, and what happens at runtime
14:17	RedNifre	I'm trying to understand what (var "bla") is. I don't understand why (def a "a") doesn't just put the string in the namespace map.
14:17	hiredman	what I said re: inlining
14:18	RedNifre	I don't understand the point about inlining.
14:18	hiredman	with a var, the lookup only needs to happen once, to get the mutable var cell, with a direct map lookup, you would need to do a map lookup for ever function call
14:19	hiredman	RedNifre: just imagine the var is a inline cache for the map value you would lookup (it isn't, but whatever)
14:19	RedNifre	Hm. I guess def replaces not the content of the var but the var itself?
14:19	hiredman	no
14:20	hiredman	vars are interned, and def will intern a new one if it does exist, but it reuses an existing one if it already does
14:21	RedNifre	If I do (def a "a") (def b a), what exactly is in b? The way I understand it a and b would point to the same var. But if I do (def a "x") a will point to a newly created var containing "x" where b will still point to the old var containing "a"?
14:21	hiredman	no
14:22	RedNifre	What exactly happens in this code then? (def a "a") (def b a) (def a "x") b ?
14:22	hiredman	(def b a) in that scenario, creates a new var b, then derefs the var a, and puts that value in b
14:22	hiredman	b will be "a" in that scenario
14:24	RedNifre	Okay, so every def creates a new var, but the (def a "x") would change the content of the already existing var that is pointed to by a from "a" to "x"?
14:24	RedNifre	I meant every def that introduces a new ... symbol ... name ...thingy.
14:24	TimMc	matt______: Oh, I don't know about the more method, lemme see...
14:24	hiredman	a simplified version of the semantics for symbol evalution for clojure is something like: to evaluate the symbol a, if a names a local, it evalautes to the value of that local, if a names a var, deref the var
14:25	hiredman	RedNifre: no, def produces a var
14:25	justin_smith	TimMc: matt______: .more is what rest calls
14:25	RedNifre	hiredman in my example, what exactly does (def a "x") do?
14:25	hiredman	RedNifre: vars generally are named by symbols (not always, but you'll likely never run in to an anonymous var)
14:26	TimMc	ah yeah, here's LazySeq's impl: https://github.com/clojure/clojure/blob/3748127f440a39d6003e94733da70c2704e385f2/src/jvm/clojure/lang/LazySeq.java#L84
14:26	RedNifre	Does (def a "a") (def a "x") change the content of the var or does it create a new var and puts it in the namespace map?
14:26	hiredman	RedNifre: it looks for a var in the namespace bound to in-ns named a, creates it if it doesn't exist, and sets its value to "x"
14:26	hiredman	RedNifre: it changes the value of the var
14:27	RedNifre	Okay. Let's see if I understand inlining then...
14:27	hiredman	RedNifre: vars are global references by the way, local bindings of names to values (via let, or function application) are locals not vars
14:27	RedNifre	If I do [a a a a], does it fetch the var from the namespace map and then kinda replaces the code with [$var $var $var $var] before continuing?
14:28	hiredman	no
14:28	RedNifre	Can you give me an example for inlining?
14:28	matt______	hm, well more doesn't call rest there. it's the same except it returns an empty list when empty.
14:28	hiredman	the compiler finds the var in the namespace map, and emits code that says "construct such and such a var
14:28	hiredman	whoops
14:29	matt______	next in RT doesn't call more, either. next calls next, more calls more.
14:29	hiredman	generate java byte code effectively has a reference to the var
14:29	hiredman	so when the function is running, it never does a map lookup
14:29	hiredman	it can find all the values it needs just by dereferencing the vars
14:30	hiredman	derefencing the vars is a simpler operation than a map lookup, so the jvm's jit is better able to optimize it
14:30	hiredman	(where it gets inlined away or not is sort of complicated)
14:31	RedNifre	Hm... I don't know much about bytecode, I guess that the Clojure code [a a a a] kinda turns into bytecode that says new Vector(Namespace.a, Namespace.a, Namespace.a, Namespace.a);?
14:31	hiredman	no
14:31	RedNifre	dammit
14:32	hiredman	(let [x (resolve 'a)] (Vector. @x @x @x))
14:32	justin_smith	matt______: no, I said rest calls .more
14:32	hiredman	really it is more like
14:32	hiredman	(let [x (resolve 'a)] (fn [] (Vector. @x @x @x)))
14:33	hiredman	like, if you had a function like (defn f [] (inc a))
14:33	justin_smith	matt______: next calls .next, more and next are alternatives to one another
14:33	justin_smith	*rest and next that is
14:33	hiredman	(let [x (resolve 'a)] (def f (fn [] (inc @x))))
14:33	RedNifre	Hmm, I think it's getting clearer.
14:34	hiredman	so you see, the resolution of 'a happens once, and then ever after whenever you call the function f, it just reads the value from the resolved var
14:36	matt______	justin_smith: thanks. seems a bit confusing, but i see it fitting together now.
14:36	RedNifre	So if I write the pseudo bytecode as java code it might compile to something like Var<Integer> x = fetchFromTheNamespaceMap("a"); Integer f() { return inc(x.get()); } ?
14:37	hiredman	sort of
14:37	hiredman	if you know java, the var resolution happens as a static init and the var is held in a static field
14:37	RedNifre	Okay, that's how I imagined it.
14:38	matt______	smells like rest, next, and more will behave the same except for the empty case, and that rest is roughly an alias for more in the empty case.
14:38	RedNifre	Does the content of a var ever change?
14:38	justin_smith	matt______: rest is .more (but might change in the future)
14:38	justin_smith	matt______: next is .next
14:38	hiredman	sure
14:39	RedNifre	how? when?
14:39	justin_smith	matt______: this is much clearer if you look at (source next) and (source rest)
14:39	hiredman	if you define a function g that invokes function f, but at some point in the repl decided to define a new f
14:39	hiredman	g will when executed use the new f
14:39	matt______	justin_smith: i'm looking at it right now at the top of core.clj before defn is available.
14:41	justin_smith	matt______: no, I mean the source actually available at runtime
14:41	justin_smith	like literally what (source rest) and (source next) return in the repl
14:41	RedNifre	oh god...
14:42	hiredman	that is also what I think of as "standard var linkage mechanics", there are varations for dynamic binding (slight), direct linking (this is new in 1.8, and basically eliminates the var at compile time), and static linking (this is a defunct, sort of a precursor to direct linking, the compiler support for it is deleted or commented out)
14:42	matt______	justin_smith: that returns the exact same thing as shown in core.clj... ?
14:42	matt______	https://github.com/clojure/clojure/blob/010864f8ed828f8d261807b7345f1a539c5b20df/src/clj/clojure/core.clj#L57
14:42	RedNifre	I haven't thought this through but it sounds like it works differently for def and defn.
14:42	hiredman	no
14:43	hiredman	defn is more or less def
14:43	matt______	the calls to (source rest) or (source next) that is.
14:43	hiredman	(the def part is, the fn part is fn of course)
14:43	justin_smith	matt______: oh, right
14:43	RedNifre	ah, never mind. I thought the wrong way...
14:44	hiredman	RedNifre: (def b a) from your ealier example comes out as (let [x (resolve 'a)] (def b @x))
14:44	hiredman	it is fairly common for people to be confused about the behavior of top level defs liek that
14:44	matt______	justin_smith: just making sure. thanks for the info.
14:45	justin_smith	RedNifre: and people that know they are confused are a step up on those that simply assume wrongly
14:46	RedNifre	Okay, so (def a "a") (def b a) is two separate vars containing the same string. But the function (defn bla [] a) ... fetches the var when it gets created... so when I later do (def a "x"), the CONTENT of the var changes from "a" to "x" which means that calling the bla function will now return "x" but the b value will still return "a"?
14:47	hiredman	yes
14:47	RedNifre	Phew!
14:48	RedNifre	I think I get it now. Thanks for your patience :)
14:52	hiredman	I have this essay I keep meaning to write entitled "Vars, what the hell?"
14:52	RedNifre	When I do (defn bla [] a), the namespace map gets a new entry called bla that points to a newly created var containing (fn [] the-var-that-was-in-a-when-this-function-got-created), right?
14:53	hiredman	more or less, but you don't really talke about the var being in a, a is the name of the var
14:54	hiredman	a doesn't have a place to store things, it is a name
14:54	justin_smith	RedNifre: that's right, and also if you deleted a with ns-unmap and made a new a, bla would never see the value of the new a
14:54	RedNifre	Well, no, if I do (def a "x") later then the function will still use the now nameless var that can no longer be found in the namespace map?
14:55	hiredman	no
14:55	RedNifre	oh right
14:55	RedNifre	dammit
14:55	justin_smith	RedNifre: you have crossed signals with hiredman because hiredman has had me on his ignore list for years
14:56	justin_smith	RedNifre: you are correct, if you ns-unmap a, then make a new a, bla never sees the new a
14:56	hiredman	(as an aside you can actually create nameless vars, but that is a feature that isn't used ever, outside of the compiler)
14:56	RedNifre	aw, now you two are being intentionally confusing. How am I supposed to chat with people that have each other on their ignore list? :)
14:57	justin_smith	RedNifre: I don't ignore him, it's one way, just telling you he didn't understand what you were saying because he didn't see what I said
14:57	ridcully	but you could tell the one, what the other siad
14:57	RedNifre	Nah, telling one what the other said would be disrespecting the ignore list ;)
14:59	RedNifre	Is this var business only for the REPL? I mean, I wouldn't redefine things in regular code, right?
14:59	justin_smith	RedNifre: there is no such thing as "only for the repl" in clojure
14:59	justin_smith	RedNifre: there's just one compiler
15:00	RedNifre	But (def a "a") (def a "b") would seem weird to me in regular code.
15:00	RedNifre	what did you do to get on the ignore list? :)
15:00	justin_smith	pragmatically, I would call that bad code. But it's legal. There are no special repl-only features or rules in the clojure compiler.
15:00	justin_smith	RedNifre: I think I was playing with clojurebot and being a dumbass, not sure
15:01	justin_smith	"dumbass" probably works as a description, whatever it was
15:01	RedNifre	Yeah, I didn't mean that it would be illegal code outside the REPL, just weird.
15:02	TimMc	justin_smith: Wait, you're on his ignore list too?
15:02	justin_smith	TimMc: yup, it's quite a club we've got isn't it
15:03	TEttinger	the ignoramancer ignores most of the channel apparently
15:04	TimMc	I at least do people the favor of clearing my ignore list periodically...
15:04	RedNifre	Another thing, JoC mentions using keywords like an enum, e.g. :north :west :south :east. That seems strange to me I like the concept of an enum being a finite set of well known values. Am I being oldfashioned? Are there regular enums?
15:05	justin_smith	Java has enums, I think you can create them via interop
15:05	TEttinger	yeah, not sure how you'd make one in Clojure
15:05	justin_smith	but usually we use keywords as if they were enums if we need something like that
15:06	RedNifre	It's all so dynamic... how do you refactor that?
15:07	justin_smith	RedNifre: a lot of clojure idioms are very dynamic, borrowed from the lisp world where compile-time checking isn't really a done thing
15:07	justin_smith	you refactor it by changing things until it doesn't look broken any more (which is the downside of the lisp approach of course)
15:07	matt______	i was linked and read "seqs and colls", and perhaps i'm dense, but i still don't understand why vectors don't implement the seq abstraction.
15:07	matt______	you can call first, next, cons on a vector, but it goes through conversions and/or an if-else-if ladder of instanceof calls in RT to get there versus just having a method on the class
15:08	matt______	anyone know the rationale?
15:08	justin_smith	matt______: cons doesn't return a vector because vectors have no built in prepend - you need to convert to another type and then back again
15:09	matt______	justin_smith: the same is true for first and rest, right?
15:09	justin_smith	afaik, yes
15:10	matt______	yet all of those will take a vector and take a slower route than just having vectors be seqs an implement the required methods.
15:10	justin_smith	matt______: clojure will kind of steer toward things that are natively apropriate for data types, even at the price of some inconveniences, I think vectors not being a seq is part of this
15:10	justin_smith	like, vector not being a seq reflects the fact that you need to do a type conversion before you can do seq things to it
15:11	justin_smith	(even if that conversion is implicit in most idiomatic code)
15:11	RedNifre	Hm, now JoC explained metadata to me but without examples... when would I use metadata as opposed to putting things into an object? Or is that for annotating data I get from other libraries?
15:12	justin_smith	RedNifre: vars are a greate example here
15:12	justin_smith	,(meta #'+)
15:12	clojurebot	{:added "1.2", :ns #object[clojure.lang.Namespace 0x7da402f4 "clojure.core"], :name +, :file "clojure/core.clj", :inline-arities #object[clojure.core$_GT_1_QMARK_ 0x2d5dbd31 "clojure.core$_GT_1_QMARK_@2d5dbd31"], ...}
15:12	matt______	justin_smith: ok. yeah, it seems like performance is the reason for not doing it. efficiently adding at the front is not doable, and even rest is... well, i'm not sure of the efficiency of subvec, but will look into it.
15:13	RedNifre	,(-> (meta #'+) :name type)
15:13	clojurebot	clojure.lang.Symbol
15:14	RedNifre	,(identical? + (-> #'+ meta :name))
15:14	clojurebot	false
15:14	RedNifre	,(identical? '+ (-> #'+ meta :name))
15:14	clojurebot	false
15:14	RedNifre	,(= '+ (-> #'+ meta :name))
15:14	clojurebot	true
15:14	RedNifre	phew
15:14	TimMc	matt______: subvec creates a window
15:15	TimMc	,(class (subvec [1 2 3 4 5] 1 2))
15:15	clojurebot	clojure.lang.APersistentVector$SubVector
15:15	matt______	TimMc: i haven't looked at the source yet, but if that's what I think it means, it's quite efficient by saying "just look between index i and j"
15:16	RedNifre	How exactly is metadata connected to things?
15:16	justin_smith	RedNifre: it's a method in IMeta, implemented using a mutable slot in the Object usually
15:16	RedNifre	Does the namespace contain a separate metadata map that has vars as keys that point to vars that point to metadata maps?
15:16	amalloy	justin_smith: no way
15:16	justin_smith	amalloy: no?
15:17	amalloy	there's no mutation for metadata
15:17	justin_smith	oh, OK, right that makes sense, my bad
15:17	amalloy	IObj/withMeta returns a new version of the object with the specified metadata
15:17	TimMc	matt______: Yeah, exactly. But it also holds onto the original, GC-wise, just like substring.
15:17	justin_smith	RedNifre: anyway, a Var implements IMeta and knows how to return its metadata
15:18	justin_smith	RedNifre: the namespace also holds metadata, but only about itself
15:18	justin_smith	,(meta ns)
15:18	clojurebot	nil
15:18	RedNifre	wait, does the metadata sit in the var or in the thing the var points to?
15:18	TimMc	https://github.com/clojure/clojure/blob/clojure-1.7.0/src/jvm/clojure/lang/APersistentVector.java#L528
15:18	justin_smith	or it can, doesn't always have any
15:18	amalloy	sorry justin_smith, 0-2 today
15:18	justin_smith	amalloy: oh, man
15:18	amalloy	,(instance? clojure.lang.IMeta #'inc)
15:18	clojurebot	true
15:18	amalloy	er
15:18	amalloy	well
15:19	justin_smith	amalloy: Vars hold their metadata, not their namespaces, I know that much!
15:19	amalloy	i guess it does implement IMeta but not IObj
15:19	TimMc	aha
15:19	amalloy	so there's no with-meta for vars
15:19	justin_smith	got it, I wasn't going that far
15:20	RedNifre	,(def pi (with-meta 2 {:description "Important number!"}))
15:20	clojurebot	#error {\n :cause "java.lang.Long cannot be cast to clojure.lang.IObj"\n :via\n [{:type clojure.lang.Compiler$CompilerException\n :message "java.lang.ClassCastException: java.lang.Long cannot be cast to clojure.lang.IObj, compiling:(NO_SOURCE_FILE:0:0)"\n :at [clojure.lang.Compiler$InvokeExpr eval "Compiler.java" 3657]}\n {:type java.lang.ClassCastException\n :message "java.lang.Long cannot...
15:20	matt______	TimMc: yeah, that makes sense. to me (which doesn't mean much), cons seems like the main hangup for vectors not being seqs.
15:20	justin_smith	RedNifre: 2 is not an IMeta
15:20	amalloy	yeah, i was confused since you were talking abotu IMeta and mutation earlier
15:20	justin_smith	or an IObj for that matter
15:20	RedNifre	What's IMeta and IObj?
15:21	justin_smith	RedNifre: the interfaces you must implement to use metadata in the normal ways
15:21	justin_smith	RedNifre: you might find it informative to look at (source meta) in your repl
15:23	TimMc	RedNifre: Metadata is stored on the object itself, it just isn't used for equality checks.
15:23	backnforth	Can someone else with out with my code.. I have a very basic clojure program thats giving me a, "Exception in thread "main" java.lang.RuntimeException: Map literal must contain an even number of forms". core.clj: http://pastebin.com/AGdXVGxM
15:24	TimMc	RedNifre: Vars are objects in their own right, and store metadata... but they also point oto other objects, which may or may not support metadata themselves.
15:24	RedNifre	Okay, so it's not truly that "meta", huh?
15:24	justin_smith	TimMc: just to be a donkey I could define a type right now that uses some external location to store its metadata :)
15:24	backnforth	When the remove the "listRead" function and just keep foo, the "lein run" works fine.
15:24	ridcully	,{:a :b :c} ; backnforth
15:24	clojurebot	#<RuntimeException java.lang.RuntimeException: Map literal must contain an even number of forms>
15:25	justin_smith	backnforth: what do you think {} does?
15:25	justin_smith	backnforth: based on your indentation, I think you assume it works the way {} does in C/java/javascript
15:25	backnforth	Same as what imperative programs do.
15:25	justin_smith	in clojure it's only used for creating hash-maps
15:26	backnforth	Yes, justin_smith
15:26	justin_smith	,{:a 0}
15:26	clojurebot	{:a 0}
15:26	justin_smith	backnforth: our closest analog to {} in java is (do) but usually you don't even need to explicitly use do
15:27	backnforth	I love Clojure, but damn can you be complicated sometimes.
15:27	RedNifre	I forgot, why do I have to do (meta #'+) instead of (meta +) again? Was it because (meta +) looks for metadata in a newly created + symbol whereas (meta #'+) looks in the content of the var of the namespace?
15:27	justin_smith	backnforth: this isn't complicated, it's actually simpler than the rules for other languages, just different
15:28	backnforth	justin_smith: I understand
15:28	justin_smith	RedNifre: because somebody attached metadata to the var, but nobody attached metadata to the function, hypothetically either or neither could have metadata
15:29	ridcully	backnforth: you want to find all x in inputList? then maybe filter is what you want here?
15:29	justin_smith	,(meta (with-meta #() {:has-meta true})) ; RedNifre
15:29	clojurebot	{:has-meta true}
15:29	backnforth	ridcully: What is filter?
15:29	RedNifre	What's #() again?
15:29	ridcully	,(doc filter)
15:29	clojurebot	"([pred] [pred coll]); Returns a lazy sequence of the items in coll for which (pred item) returns true. pred must be free of side-effects. Returns a transducer when no collection is provided."
15:29	justin_smith	,'#()
15:29	clojurebot	(fn* [] ())
15:29	justin_smith	RedNifre: ^
15:30	RedNifre	gaah
15:30	RedNifre	What's fn* then?
15:30	justin_smith	RedNifre: an implementation detail of fn
15:30	RedNifre	I think my head is getting full.
15:30	justin_smith	fair enough - pretend it is fn, it might as well be in this case
15:30	justin_smith	RedNifre: kudos on the curiosity, btw
15:31	backnforth	ridcully: I'm looking to return the indexs, not the items
15:31	RedNifre	I'm not quite sure about the relation of # and lambdas. I mean #(println "hey") is kinda a lambda. And if #() returns () I would guess that #'+ returns '+ ? Or is that a different # ?
15:32	TimMc	RedNifre: #( is a single piece of syntax
15:32	TimMc	Check out http://clojure.org/reader, it's called a reader macro. (No, you can't really define your own.)
15:33	TimMc	,'#(println "thing:" %) ; RedNifre: See how it just expands to a fn
15:33	clojurebot	(fn* [p1__143#] (println "thing:" p1__143#))
15:33	TimMc	I quoted it so you could see the expansion.
15:34	RedNifre	,'#()
15:34	clojurebot	(fn* [] ())
15:34	RedNifre	Okay, that one makes sense.
15:34	RedNifre	,#'+
15:34	clojurebot	#'clojure.core/+
15:34	RedNifre	That # is completely unrelated to #( right?
15:35	TimMc	who reads the reader
15:36	TimMc	RedNifre: # is a dispatch character; the next character after it determines what piece of syntax you're using.
15:38	RedNifre	Ah. I thought that #'+ means something like # '+ i.e. there's a quoted + in there, but it's actually #' +
15:39	RedNifre	,(meta (var +))
15:39	clojurebot	{:added "1.2", :ns #object[clojure.lang.Namespace 0x7b99e11e "clojure.core"], :name +, :file "clojure/core.clj", :inline-arities #object[clojure.core$_GT_1_QMARK_ 0x3286c02d "clojure.core$_GT_1_QMARK_@3286c02d"], ...}
15:40	RedNifre	I think I get it now.
15:40	amalloy	RedNifre: right. i wouldn't be surirised to learn that the #' dispatch was chosen because it looks a bit like a different kind of quote
15:41	amalloy	,(:added (meta #'+)) ;; lies
15:41	clojurebot	"1.2"
15:41	RedNifre	The ":name +" part in (var +)'s metadata implies to me that two separate keys in the namespace map will never ever point to the same var. Is that correct?
15:44	RedNifre	It's all getting clearer... how do I print the current namespace's symbol-var-map ?
15:45	amalloy	,(take 5 (shuffle (ns-publics (the-ns 'clojure.core))))
15:45	clojurebot	#error {\n :cause "clojure.lang.PersistentHashMap cannot be cast to java.util.Collection"\n :via\n [{:type java.lang.ClassCastException\n :message "clojure.lang.PersistentHashMap cannot be cast to java.util.Collection"\n :at [clojure.core$shuffle invokeStatic "core.clj" 6988]}]\n :trace\n [[clojure.core$shuffle invokeStatic "core.clj" 6988]\n [clojure.core$shuffle invoke "core.clj" 6988]\n [...
15:45	amalloy	so much for shuffle
15:45	amalloy	,(take 5 (ns-publics (the-ns 'clojure.core)))
15:45	clojurebot	([primitives-classnames #'clojure.core/primitives-classnames] [+' #'clojure.core/+'] [decimal? #'clojure.core/decimal?] [restart-agent #'clojure.core/restart-agent] [sort-by #'clojure.core/sort-by])
15:46	RedNifre	,(ns-publics ns)
15:46	clojurebot	{}
15:47	RedNifre	,(def content "have to be quick")
15:47	clojurebot	#'sandbox/content
15:47	RedNifre	,(ns-publics ns)
15:47	clojurebot	{content #'sandbox/content}
15:48	RedNifre	Now it's getting really interesting :)
15:49	RedNifre	Hang on, if the namespace is already called "sandbox" why does it say #'sandbox/content? Isn't that kinda redundant?
15:49	RedNifre	(sandbox/content)
15:49	RedNifre	,(sandbox/content)
15:49	clojurebot	#error {\n :cause "java.lang.String cannot be cast to clojure.lang.IFn"\n :via\n [{:type java.lang.ClassCastException\n :message "java.lang.String cannot be cast to clojure.lang.IFn"\n :at [sandbox$eval215 invokeStatic "NO_SOURCE_FILE" 0]}]\n :trace\n [[sandbox$eval215 invokeStatic "NO_SOURCE_FILE" 0]\n [sandbox$eval215 invoke "NO_SOURCE_FILE" -1]\n [clojure.lang.Compiler eval "Compiler.java...
15:49	RedNifre	,sandbox/content
15:49	clojurebot	"have to be quick"
15:49	RedNifre	,content
15:49	clojurebot	"have to be quick"
15:50	RedNifre	Or is that just a feature of the ns-publics function?
15:51	RedNifre	,(ns-publics ns)
15:51	clojurebot	{}
15:54	RedNifre	Are Vars objects? If so, how can I inspect member variables and methods?
15:55	TEttinger	,(.hashCode +)
15:55	clojurebot	459507496
15:56	RedNifre	Is that the hashCode of the function or of the var?
15:57	RedNifre	,(.hashCode (var +))
15:57	clojurebot	1638383430
15:57	RedNifre	aha
15:58	TEttinger	,(.hashCode #'+)
15:58	clojurebot	1638383430
15:58	TEttinger	,(class #'+)
15:58	clojurebot	clojure.lang.Var
15:59	TEttinger	,(class +)
15:59	clojurebot	clojure.core$_PLUS_
15:59	TEttinger	gah this is a headache
15:59	RedNifre	Is $_PLUS_ a fake class symbolizing the native operator?
16:00	RedNifre	Anyway, how to list the public member variables and methods of objects, e.g. vars?
16:01	RedNifre	Can I look into the + Var and see a member variable pointing to the _PLUS_ function and another member variable containing a map of the metadata?
16:05	matt______	RedNifre: If you eye up https://github.com/clojure/clojure/blob/clojure-1.7.0/src/jvm/clojure/lang/Var.java ...
16:05	sdegutis	How do you match an alphabetic character of any case using Clojure regex?
16:05	sdegutis	I currently have this monstrosity: #"[a-zA-Z]" but I think that's not ideal.
16:06	matt______	You'll see it has root, sym, and ns fields
16:06	RedNifre	sdegutis #"(?i)[a-z]" ?
16:06	sdegutis	Hmm but isn't there something like \w ?
16:06	matt______	,(.-ns #'+)
16:06	clojurebot	#object[clojure.lang.Namespace 0xf093f2 "clojure.core"]
16:07	matt______	Or to get what it points to, (.get #'+)
16:07	RedNifre	yeah, that's even better
16:07	sdegutis	No watch, \w matches numbers too.
16:07	sdegutis	Oh well I guess that's fine.
16:07	RedNifre	matt I meant from within clojure.
16:08	ystael	sdegutis: #"\p{L}" matches anything with the Unicode property Letter, I think
16:08	sdegutis	Cool, thanks.
16:08	sdegutis	Good day everyone.
16:08	sdegutis	Good day.
16:08	matt______	That (.get #'+) call is within clojure. perhaps i'm misunderstanding.
16:08	RedNifre	I meant getting a list of all public variables and methods.
16:09	RedNifre	A bit like when you inspect the current namespace
16:09	RedNifre	,(ns-public ns)
16:09	clojurebot	#error {\n :cause "Unable to resolve symbol: ns-public in this context"\n :via\n [{:type clojure.lang.Compiler$CompilerException\n :message "java.lang.RuntimeException: Unable to resolve symbol: ns-public in this context, compiling:(NO_SOURCE_PATH:0:0)"\n :at [clojure.lang.Compiler analyze "Compiler.java" 6688]}\n {:type java.lang.RuntimeException\n :message "Unable to resolve symbol: ns-pu...
16:09	RedNifre	,(ns-publics ns)
16:09	clojurebot	{}
16:09	RedNifre	,(def resetting "all the time")
16:09	clojurebot	#'sandbox/resetting
16:09	RedNifre	,(ns-publics ns)
16:09	clojurebot	{resetting #'sandbox/resetting}
16:09	matt______	ok, i see. i know what i'd try wouldn't work.
16:10	matt______	,(.getMethods (class (var x)))
16:10	clojurebot	#error {\n :cause "Unable to resolve var: x in this context"\n :via\n [{:type clojure.lang.Compiler$CompilerException\n :message "java.lang.RuntimeException: Unable to resolve var: x in this context, compiling:(NO_SOURCE_PATH:0:0)"\n :at [clojure.lang.Compiler analyzeSeq "Compiler.java" 6875]}\n {:type java.lang.RuntimeException\n :message "Unable to resolve var: x in this context"\n :at ...
16:10	matt______	Whoops
16:10	matt______	,(.getMethods (class (var +)))
16:10	clojurebot	#object["[Ljava.lang.reflect.Method;" 0x30bb067 "[Ljava.lang.reflect.Method;@30bb067"]
16:10	RedNifre	Yeah, but that's the java way. Is there an idiomatic clojure way?
16:11	matt______	not that i'm aware of, but that doesn't mean there isn't.
16:12	amalloy	see the clojure.reflect namespace
16:12	amalloy	of course be aware that using reflection to peek inside of objects is taking you well outside documented APIs
16:14	RedNifre	When examining my REPL's namespace I found a clojure_two.core.proxy$java.lang.Object$SignalHandler$d8c00ec7, what's that?
16:14	RedNifre	type gives java.lang.Class, how can I poke it some more?
16:15	RedNifre	"clojure_two" is the lein project's name in which's folder I started the REPL.
16:18	matt______	amalloy: nice.
16:19	matt______	RedNifre: that's something repl-related to handling interrupts.
16:19	sdegutis	The past 20 minutes have been wasted trying to parse minified CSS via regular expressions. Let that be a lesson to you.
16:20	RedNifre	"Never touch anything related to CSS or HTML, ever", got it.
16:22	sdegutis	RedNifre: On the contrary, I wrote in about 80 lines a Clojure version of SASS or Less.
16:22	sdegutis	RedNifre: and it's been a huge productivity boost.
16:22	sdegutis	RedNifre: it's the opposite thing that's proving to be a challenge: parsing minified CSS to turn it into Clojure forms.
16:22	RedNifre	"Become a web developer today", got it.
16:22	sdegutis	RedNifre: i like ur style
16:23	RedNifre	So you can now write CSS in edn?
16:23	sdegutis	Me? Sure.
16:23	sdegutis	You? No. Unless you write the same 80 lines I wrote.
16:24	sdegutis	And I get to use everything in clojure.core, too. Yay!
16:25	RedNifre	Uh, why do you turn minified CSS into Clojure?
16:26	sdegutis	RedNifre: Because we didn't always start with Clojurified CSS. In the old days, I actually had to write plain literal CSS by hand.
16:26	RedNifre	Sure, but why is it minified?
16:26	sdegutis	RedNifre: Now I want to convert some of that to my Clojure-CSS data structures, so that I can work more quickly with it.
16:27	sdegutis	RedNifre: because it was minified.
16:27	RedNifre	"Minifying CSS is a destructive process", got it :P
16:27	sdegutis	Oh good point though, maybe I can find my before-minifying version of it in the git history.
16:27	RedNifre	:)
16:27	sdegutis	But that assumes I haven't altered the minified version since minifying it.
16:27	sdegutis	Which I vaguely remember maybe doing possibly.
16:28	RedNifre	Ah, gotta go, my head is full for today.
16:29	sdegutis	:)
16:29	RedNifre	See you guys tomorrow!
16:30	sdegutis	We'll see.
17:05	justin_smith	amalloy: I think you were wrong and the metadata on vars is actually mutable. If I use def to define something, and then cache the var with another def, then define again and add metadata, the old var still equals the var, but the var now has different metadata, and the cached var has the metadata applied now, which makes me think mutation must have happened
17:06	amalloy	oh on vars it is
17:06	amalloy	and other refs
17:06	justin_smith	amalloy: yeah, maybe I was overgeneralizing before, because I was really thinking about the var case
17:06	justin_smith	because meta on def would be weird otherwise
17:07	amalloy	would it? def could just replace the var wholesale
17:07	amalloy	but i guess that would break other code that depends on this namespace
17:07	amalloy	who are hanging onto Var objects
17:07	justin_smith	it could at least, yeah
17:08	justin_smith	eg. running a def again would not change behavior of functions in other namespaces (unlike now), but only when you apply new metadata (which could be a line number change)
18:06	matt______	i'm trying to extend a protocol to hit arrays of any type. the primitives work, but Object[] is not catching things that derive from it. any insights?
18:10	matt______	to clarify, I can extend [Ljava.lang.Object, which works fine on (make-array java.lang.Object n), but doesn't work on (make-array java.lang.String n)
18:19	justin_smith	matt______: yeah, I don't think [Ljava.lang.String; extends [Ljava.lang.Object; so the extension won't be inherited
18:20	matt______	But it does. https://docs.oracle.com/javase/7/docs/api/java/lang/String.html
18:20	justin_smith	matt______: what about extending java.util.List instead, and doing the extra steps to get an ArrayList or whatever?
18:21	justin_smith	matt______: String does inherit Object, [Ljava.lang.String; does not extend [Ljava.lang.Object; - arrays are barely if at all OO
18:22	matt______	justin_smith: ah, i see what you're saying about the [L-prefixes now, ok.
18:22	justin_smith	matt______: it's not even a prefix, it's part of the name of a completely different type (that isn't even a class iirc, arrays are not like other things)
18:22	justin_smith	or maybe it is a Class, I forget the details
18:24	matt______	justin_smith: i will probably end up using some sort of j.u.Collection, but was hoping for the extra performance if it wasn't too difficult.
18:27	justin_smith	matt______: maybe check out Arrays/asList which returns a fixed size List that uses the array for the actual data - it's just a thin wrapper, but gives you a List which you can trivially extend with your protocol
18:27	justin_smith	matt______: or just make sure all the arrays are arrays of Object I guess :)
18:27	justin_smith	,(into-array Object ["a" "b" "c"])
18:27	clojurebot	#object["[Ljava.lang.Object;" 0x449e153b "[Ljava.lang.Object;@449e153b"]
18:29	justin_smith	given this is clojure, you don't lose much by casting to Object anyway, it's not like we are being careful about our types in general.
18:30	matt______	justin_smith: i think you've solved it.
18:30	justin_smith	which, the asList?
18:30	matt______	well, i will look at it, but an array of Object
18:31	justin_smith	ahh, yeah, if you control the creation step of the array, that might just be your guy
18:32	matt______	just trying to make a toy data structure that mocks how clojure's work, but based on protocols and deftypes
18:32	matt______	seeing as clojure uses Object[], that seems like the way to go
18:34	justin_smith	cool project, any plans to make a blog post or tutorial out of it?
18:35	matt______	umm, maybe. i wrote up a bit about protocols mostly for my friends the other day, so this will probably grow into that eventually.
18:37	matt______	it started as "all these interfaces have 1-3 methods. how hard could it be to write something like clojure's vector in terms of protocols/deftypes?" famous last words.
18:38	justin_smith	haha, nice
18:54	amalloy	well, that's what cljs did already, right?
19:16	matt______	amalloy: yeah, except those aren't toys. :)
19:17	matt______	and a bit different, too. js arrays are a bit more flexible that java arrays, but they lose a lot to JS' typing.
19:36	ddellacosta	amalloy: is lazybot down for the count?
19:37	ddellacosta	>
20:11	TimMc	yep
20:15	rhg135	dead. deeeeeeeeeeeeeeeead
20:35	madmax88	So has anyone has problems where a jar made with `lein uberjar` isn't writing a file, but when you use `lein run`, the program will?
20:37	madmax88	My program also writes to a file with `lein trampoline run`. But, when running a jar with `lein uberjar`, the file gets created, but remains blank
20:49	madmax88	found the problem: I needed to call `(shutdown-agents)`
21:07	TimMc	yuuup
21:07	TimMc	although... no, I don't understand why it would have that effect
21:10	matt______	interesting: though small, the clj and cljs ISeq interface/protocol differ quite greatly! first, next, more, and cons in clojure compared to just first and rest in cljs.
21:15	amalloy	well in clojure, ISeq inherits methods from parent interfaces
21:15	amalloy	in cljs the protocols are a la mode
21:15	amalloy	a la carte
21:15	amalloy	not covered with ice cream or modern
21:18	matt______	amalloy: sure, but it still adds two methods that need to be implemented and (roughly) renames another compared to the cljs version.
21:19	amalloy	not really. more and next are the same thing, and cons is part of another protocol that every implementation of ISeq will also implement
21:19	matt______	and if you look at the history, cljs did have both next and rest for a hot minute, but never had the oft-forgotten more.
21:20	matt______	amalloy: more and next are the same except when they're not. :)
21:20	amalloy	well yes
21:20	matt______	(not= (more (seq [])) (next (seq [])))
21:21	matt______	(that was news to me. maybe you even told me. :)
21:21	amalloy	right, more is rest, and next is next
21:21	amalloy	as i recall
21:23	matt______	still interesting to see the differences.